Radical cation states of 2,3,5,6‐tetramethylenenorbornane, 2,3,5,6‐tetramethylenebicyclo[2.2.2]octane and of related compounds

The He(Iα) photoelectron spectra of 2,3,5,6‐tetramethylenebicyclo[2.2.1]heptane (1), 2,3,5,6‐tetramethylene‐7‐oxabicyclo[2.2.1]heptane ( 2 ), 2,3,5,6‐tetramethylenebicyclo[2.2.2]octane ( 3 ) and 5,6,7,8‐tetramethylenebicyclo[2.2.2]oct‐2‐ene ( 4 ) are presented. The assignments for the highest 4 or 5 π‐bands are made on the basis of LCBO and SPINDO calculations for compounds 1, 3 and 4 . The results confirm the spectroscopic assignment of Klessinger et al. for the lower members of the series. Finally, the localized orbitals derived from SPINDO results, are used to discuss the “through‐bond” and “through‐space” interaction pattern in molecules 1, 3 and 4 .